Method to recover the exposure sensitivity of chemically amplified resins from post coat delay effect

ABSTRACT

Methods of fabricating a photomask, methods of treating a chemically amplified resist-coated photomask blank, a photomask blank resulting from the methods, and systems for fabricating a photomask are provided. The method is useful for recovering the exposure sensitivity of a chemically amplified resist disposed on a photomask blank from a post-coat delay effect.

FIELD OF THE INVENTION

The invention relates generally to semiconductor processing methods, andmore particularly to processes for fabricating a photomask that can beused in a photolithography process.

BACKGROUND OF THE INVENTION

Photolithography using a patterned masking layer is commonly used forformation of electronic components such as semiconductor integratedcircuits. A pattern is transferred to a reactive photoresist layer onthe semiconductor substrate by exposure of the patterned masking layeroverlying the substrate to light or other energy source (such asultraviolet light or electron beam radiation) which passes through openareas of the patterned masking layer.

The masking layer can be, for example a photomask or reticle, preparedfrom a photomask blank that typically comprises a thin layer of anopaque or nontransparent material, typically a metal-containing materialsuch as a chromium-, molybdenum- or tungsten-containing material,deposited on a transparent plate of glass or quartz by sputtering orvacuum evaporation, for example. A pattern can be formed on thephotomask blank structure by standard photolithography processes toselectively remove portions of the nontransparent layer (e.g., opaquechromium film) and create open areas. The pattern can be etched, forexample, by forming a photoresist material over the nontransparentlayer, forming a pattern in the photoresist material with an electronbeam or laser beam, and transferring the pattern to the underlyingnontransparent material with an etch that removes exposed portions ofthe nontransparent material.

With the fast pace of reduction of the micro-lithography design rule andthe significant increase of data volume, the requirement on criticaldimension (“CD”) control and throughput on a photomask manufacture isbecoming more and more challenging. Currently, photomasks are patternedwith either 50 kV e-beam or laser pattern generation tools, andchemically amplified photoresists (“CA resists”) that are sensitive toshorter wavelengths of light are being used to reduce the beam exposure(dose) and settling times, thereby improving the throughput of photomaskpattern exposure. CA resists are more sensitive to radiation thannon-chemically amplified resists such as ZEP-7000, thus needing asmaller dose of radiation (e.g., 8–9 μcoulomb versus about 25 μcoulomb)and a shorter development time.

Typical CA resists are composed of an acid generator that produces acidupon exposure to radiation (e.g., ultraviolet (UV) light, laser light,X-rays, electron beam), and acid-labile compounds or polymers that havechanged solubility in a developer solvent through acid-catalyzedreactions. The irradiated area forms an image in the CA resist, and anannealing step (post exposure bake, or PEB) is performed after exposure.The photoresist is then exposed to a developing solvent to removeportions of the resist, the underlying opaque chrome or othernontransparent layer is etched, and the CA resist is removed. Thepatterned photomask is used to transfer a pattern to a photoresist layerdisposed on a wafer during a fabrication step. The patterned photomasklayer is exposed to blanket radiation that passes through open areas ofthe photomask layer onto the surface of the photoresist. The photoresistis then developed providing open areas exposing a material layer on thewafer. A fabrication step, for example, an ion implantation or an etchof the material layer, can be performed to form an underlyingsemiconductor device structure.

Ideally, it is advantageous to coat the photomask blank with a CA resistand immediately expose the resist on the blank. However, in practice,resist-coated blanks are often stored for several hours up to weeksbefore exposure. A difficulty with the use of CA resists is the changein stability and radiation dose sensitivity that occurs when a CA resistis coated on a substrate that is left standing inside or outside anirradiation apparatus. This effect is commonly known as “post coatdelay” (PCD) effect.

Development of CA resists depends on the catalytic action of the acidgenerator, and if acid loss (neutralization) occurs, which decreases theradiation dose sensitivity of the resist, abnormalities will occurduring pattern formation resulting in a significant difference betweencritical dimensions (CD) (i.e., minimum feature dimensions) of thepatterned features compared to the required pattern dimensions. The acidloss is believed to be due to the presence of nitrogen-containingcompounds such as atmospheric ammonia or ammonium ions, which neutralizethe acid generator resulting in incomplete solubility of the resist,thus limiting shelf life of a photomask blank with an applied CA resistlayer.

Typically, to compensate for the loss in sensitivity, the amount ofdecrease in dose sensitivity over time is estimated and the exposureprocess is adjusted accordingly. The relative dose sensitivity of the CAresist layer can be determined through experimentation and/ortheoretical calculation. The difference in dose sensitivity may be alinear function of time difference between exposure of regions, alogarithmic difference, or related by some other mathematicalcorrelation, depending on the type of radiation utilized, the type ofresist utilized, and the tolerance for differences in minimum featuresize between a first blank and a second blank.

Several methods have been used in an attempt to extend the shelf time orlength of time a photomask substrate with a CA resist applied can bestored prior to exposure to the imaging/patterning radiation. Suchmethods have included the use of protective coatings and treatment withoxygen plasma to reduce the exposure of a CA resist tonitrogen-containing compounds. While use of these known methods producessome improvement over an untreated substrate, significant profiledefects are still evident.

It would be desirable to develop a process for reducing the PCD effecton a chemically amplified (CA) resist coating disposed on a substratesuch as a photomask blank.

SUMMARY OF THE INVENTION

The present invention provides methods of fabricating a photomask,methods of treating a chemically amplified resist-coated photomaskblank, a photomask blank resulting from the methods, and systems forfabricating a photomask.

In one aspect, the invention provides, in a method of fabricating aphotomask, a method of recovering exposure sensitivity of a chemicallyamplified resist disposed on a photomask blank from a post-coat delayeffect. In one embodiment, the method comprises heating the photomaskblank to dehydrate the resist, and cooling the photomask blank in anitrogen-purged environment to about room temperature, such that theresist has a level of exposure sensitivity approximate to the resist aswhen initially applied onto the photomask blank; and patterning an imageinto the photoresist. For the heating step, for example, theresist-coated photomask blank can be positioned in a chamber that isheated to up to about 80° C. above room temperature or, in a preferredembodiment, the photomask blank can be supported on atemperature-controllable substrate (e.g., hotplate) and heated to about90–180° C. for up to about 30 minutes. In the cooling step, for example,the heated photomask blank can be positioned in a nitrogen-purgedchamber on a chill plate and cooled to about room temperature for about10–30 minutes or more. In a preferred cooling step, the heated photomaskblank is positioned in a nitrogen-purged chamber at about roomtemperature and cooled over an extended time period of about 6–12 hours.

In another aspect, the invention provides a method of treating achemically amplified resist-coated photomask blank. In one embodiment,the method comprises heating the photomask blank to dehydrate thechemically-amplified layer, prior to patterning the resist. The treatedresist layer possesses a level of exposure sensitivity approximate tothe level of the resist when initially coated onto the photomask blank.

In another aspect, the invention provides a system for fabricating aphotomask. In one embodiment, the system comprises a unit for treating achemically amplified resist layer disposed on a photomask blank prior topatterning the resist layer, the treating unit comprising: means forsupporting the photomask blank within a chamber of the treating unit,and a heating element (means). In one embodiment of the system, theheating means comprises an apparatus operable to heat the chamber to anelevated temperature. In another embodiment, the system comprises aheating element incorporated into the supporting means, which preferablycomprises a temperature controllable plate having concentric heatersdisposed on a plate with the temperature of each of the heaters beingcontrolled independently.

The system can further comprise a unit for cooling the resist layer onthe photomask blank, the cooling unit comprising: means for supportingthe photomask blank within a chamber of the cooling unit; means forpurging nitrogen from the chamber; and a cooling element (means). In oneembodiment, the cooling means comprises an apparatus operable to cootthe chamber to at least about room temperature. In another embodiment,the system comprises a cooling element incorporated into the supportingmeans, for example, a chill plate.

In an embodiment of a system according to the invention, a treating unitis provided that comprises a support platform for the photomask blankthat incorporates a temperature adjustable element that can provide bothheating and cooling; and a mechanism for purging nitrogen from thechamber. In another embodiment, the treating unit comprises a supportfor the photomask blank that incorporates an adjustable heating element;a device for maintaining the temperature of the chamber at about roomtemperature; and a mechanism for purging nitrogen from the chamber. Thetemperature controlled chamber can be used to maintain the temperatureof the chamber and a N₂-purged environment. The system can also bestructured with a unit for heating the photomask blank and a separateunit for chilling the photomask blank before patterning.

In another aspect, the invention provides a photomask blank. In oneembodiment, the photomask blank comprises an unpatterned,chemically-amplified resist layer coated on the photomask blank for anextended time and thus subjected to post coat delay effect, the resistlayer being heat-treated and substantially dehydrated such that theresist has a level of exposure sensitivity approximate to the resist aswhen initially applied onto the photomask blank.

The present invention solves the problem of maintaining a uniform andreproducible pattern critical dimension in a CA resist from the time ofapplication of the resist onto a substrate to and during a writingprocess for imaging a photomask. The process of the inventioneliminates, or substantially reduces, the sensitivity of a CAphotoresist to the environment and maintains the pattern criticaldimension of the resist to extend the shelf life of the CA resist duringstorage in handling which may be for a time period up to weeks, andduring direct write imaging of the photoresist by either optical ore-beam radiation. The process of the invention significantly improvesthe lithographic performance in terms of critical dimension andintegrity of the photoresist. The invention advantageously eliminatesunnecessary work to calibrate the post coat delay (PCD) effect, andincreases the accuracy and reproducibility of CD performance.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings, which are forillustrative purposes only. Throughout the following views, thereference numerals will be used in the drawings, and the same referencenumerals will be used throughout the several views and in thedescription to indicate same or like parts.

FIGS. 1–3 are diagrammatic cross-sectional views of a fragment of aphotomask blank at sequential processing steps showing treatment of achemically-amplified resist layer according to an embodiment of themethod of the invention. FIG. 1 illustrates a resist-coated photomaskblank at a preliminary processing step. FIG. 2 depicts a heat treatmentto dehydrate the resist layer on the photomask blank. FIG. 3 depicts aprocessing step to pattern the resist layer.

FIG. 4 is a top plan view of a prior art heating device.

FIG. 5 is a block diagram of an embodiment of a system according to theinvention incorporating a unit for treating a chemically amplifiedresist layer disposed on a photomask blank.

FIG. 6A–6B are depictions of embodiments of a treating unit that can beutilized in the system of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The invention will be described generally with reference to the drawingsfor the purpose of illustrating the present preferred embodiments onlyand not for purposes of limiting the same. The figures illustrateprocessing steps for fabricating photomask in accordance with thepresent invention. It should be readily apparent that the processingsteps are only a portion of the entire fabrication process.

In the current application, the terms “semiconductive substrate”,“semiconductor substrate”, “wafer fragment” or “wafer” will beunderstood to mean any construction comprising semiconductive material,including but not limited to bulk semiconductive materials such as asemiconductor wafer (either alone or in assemblies comprising othermaterials thereon), and semiconductive material layers (either alone orin assemblies comprising other materials). The term “substrate” refersto any supporting structure, including, but not limited to, thesemiconductive substrates described above.

The terms “photomask blank” or “patterned masking layer,” as usedherein, refers to either a photomask or reticle as those terms are knownand used in the art.

The present invention addresses and solves problems of deterioration ofradiation dose sensitivity of a chemically amplified (CA) photoresistlayer coated on a photomask blank.

FIGS. 1–3 illustrate steps in an embodiment of a method of theinvention. Referring to FIG. 1, a portion of an embodiment of aresist-coated binary photomask blank 10 is shown in cross-sectionalview. The photomask blank 10 comprises a substrate 12 and anontransparent film 14 formed on the surface 16 of the substrate 12, anda CA resist layer 18 formed on the nontransparent film layer 14. Thesubstrate 12 typically comprises a quartz plate as the base of the maskblank, but can comprise a fluorinated quartz, borosilicate glass, sodalime glass, for example, or other substantially transparent material.The nontransparent film 14 typically comprises an opaquechrome-containing layer. The layer of opaque chromium is generally about50–120 nm thick, with commercially available chromium thicknesses ofabout 50, 79, and 100 nm. The opaque chromium layer can be formed on thesubstrate by known techniques such as by reactive sputtering or vacuumevaporation. In the illustrated embodiment, an opaque chrome layer isdisposed on a quartz plate, but it is understood that the nontransparentlayer can be separated from the substrate by various interveningmaterials.

The CA photoresist layer 18 can be formed over the nontransparent layer14 by suitable means known and used in the art, for example, by spinningthe CA resist material onto the surface of the nontransparent layer. Inthe illustrated embodiment, the photoresist layer 18 is disposed on thenontransparent layer 14 but can be separated from the nontransparentlayer by various materials, for example, an anti-reflective coating(ARC) (not shown), among others. Exemplary ARC materials include chromeoxynitride, titanium nitride, silicon nitride, or molybdenum silicide,or other material suitable for use to reduce light reflection from thesubstrate surface into the resist during photolithography. Inorganic ororganic ARCs can be used. A suitable means of forming the ARC is tosputter it onto the surface of the layer.

The relative time difference between application of the CA resist layer18 on the photomask blank and exposure of the CA resist to radiationdevelopment can be up to 24 hours or more to up to several weeks, forexample, with a resulting deterioration in dose sensitivity of the CAresist.

According to the invention, prior to loading the resist-coated photomaskblank 10 onto a pattern generation tool, a process step is conducted torecover or restore the dose sensitivity of the CA resist to about thedose sensitivity level of the CA resist as initially coated on theblank. It has been found that heating of the CA resist layer on thephotomask blank prior to a radiation exposure step dehydrates the resistlayer and eliminates the need to compensate for the PCD effect and thedeterioration of the dose sensitivity of the resist material, whichwould otherwise require increasing the radiation dosage level duringpattern generation. The heating step, depicted in FIG. 2, thus improvesthe reliability of the resist.

In one embodiment, the heating step comprises placing the CAresist-coated photomask blank 10 into a nitrogen-purged environment(e.g., container) at an elevated temperature effective to heat (arrows20) the CA resist layer 18 and dehydrate the resist. Generally, thetemperature within the nitrogen-purged environment is maintained atabout 1° C. to about 80° C. above room temperature (i.e., 20° C.), orabout 21° C. to about 100° C., with a preferred temperature of about 50°C. The resist-coated blank 10 can be maintained in the heatednitrogen-purged environment to dehydrate the CA layer, which can rangefrom about 180 seconds up to about 180 minutes, for example, dependingon the time period from when the resist was initially applied to thephotomask blank, the thickness of the resist layer, the resist used,among other factors. The CA resist-coated blank can be stored in theheated, nitrogen-purged container for an extended period of time until asubsequent patterning step.

In a preferred embodiment, the heating step of the invention comprises abake treatment of the CA resist-coated photomask blank 10 to dehydratethe CA resist layer 18 prior to exposing the CA resist layer topatterning radiation. The baking step (FIG. 2) comprises exposing theresist-coated photomask blank 10 to a temperature of about 90° C. toabout 180° C., typically about 120° C. to about 140° C., for a timeperiod of about 30 seconds to about 30 minutes, preferably about 5 toabout 10 minutes. The bake step can be conducted in either a N₂-purgedor atmospheric environment.

The baking step can be conducted using the same equipment as utilized ina post-exposure bake (PEB) technique, which commonly employs atemperature-controlled plate (e.g., hotplate). A preferred bake unit isdescribed, for example, in U.S. Pat. No. 6,441,351 (Hayasaki), thedisclosure of which is incorporated by reference herein, and illustratedin FIG. 4. As shown, an exemplary bake unit 22 comprises threeconcentric heaters 24 provided in a heat equalizing plate 26. Thetemperature of each of the heaters 24 is controlled independently by anembedded thermocouple to provide a homogeneous bake treatment of the CAresist layer. A heat treatment device having a single ring heater as theheat source (not shown) can also be used.

The subsequent writing or patterning step typically takes about 3–20hours and precise pattern placement on the CA resist layer 18 is acritical consideration in preparing the photomask. Normally, the actualalignment of the pattern on the CA resist layer is offset to some extentfrom the set data points for pattern placement, commonly known as a“registration offset.” The thermal effect from a heated photomask blankcan interfere with pattern placement accuracy and increase theregistration offset.

To reduce such thermal effects, the photomask blank can be cooled,preferably to about room temperature (i.e., about 20–25° C.). Thephotomask blank can be cooled, for example, by transferring the heatedphotomask blank to a chill plate that is set at about room temperatureto cool the photomask blank for about 10–30 minutes or more. In apreferred cooling step, the photomask blank is maintained in anitrogen-purged environment (e.g., chamber, container) at about roomtemperature for an extended time period to acclimate the photomask blankto about room temperature, which is generally about 6 hours to up toabout 12 hours. Cooling of the resist layer helps prevent distortion ofthe etch pattern and loss of image quality, and helps ensure that thepattern is properly transferred to the resist.

Referring to FIG. 3, the photomask blank 10 is then patterned byexposure of the CA resist to radiation in a direct write process thatproduces an image in the CA resist, for example, using laser-producedultraviolet (UV) radiation, including deep ultraviolet (DUV) radiation,or electron beam (e-beam) radiation. Exposure of the CA photoresist toradiation will cause release of a catalyst (typically acid) within aregion of the resist, which will subsequently catalyze chemicalreactions to change the solubility of the region in a developer solventrelative to the solubility of an unexposed region.

After exposure of the CA resist to e-beam radiation, for example, thephotomask blank is transported to a bake unit and “baked” at a suitabletemperature to enhance (i.e. speed up) the chemical reaction within theCA resist so that the image will be transferred throughout the entirethickness of the CA resist and the pattern can be subsequently properlydeveloped. The bake treatment is typically referred to as a “PostExposure Bake” (PEB).

Subsequent to the bake step, the CA resist layer can be patterned anddeveloped using standard lithography techniques to form openings 28 inthe resist layer 18. Typically the CA resist layer is exposed to adeveloping solvent applied over the surface of the resist, for example,by a spinning technique. In the use of a positive CA resist, theradiation exposed areas of the resist are removed to produce open spaces28 leaving non-irradiated areas in place over the nontransparent layer14 (e.g., opaque chrome layer). In the use of a negative CA resist, theunexposed areas of the resist are removed, leaving the radiation exposedareas in place. A pattern transfer from the CA 18 resist into theunderlying nontransparent layer 14 is then performed, typically using ananisotropic plasma dry etching technique, to create openings in thenontransparent layer that expose the substrate. The CA resist is thenstripped away using known techniques in the art.

The resulting photomask is used to transfer a pattern to a photoresistlayer disposed on a wafer during a fabrication step. The photomask isexposed to blanket radiation that passes through the open areas onto thesurface of the photoresist. The photoresist is then developed providingopen areas exposing the underlying material layer on the wafer, and anion implantation or an etch of the material layer can be performed, forexample, to form an underlying semiconductor device structure. Thephotomask can be utilized in the photolithography of a semiconductordevice such as a logic device, microprocessor, DRAM, SRAM, and the like.

Subsequent processing may then be conducted on the semiconductor devicestructure, as known in the art.

FIG. 5 is a diagram of an embodiment of a system 30 that can be utilizedin implementing the method of the invention. The system 30 can include aprocessing unit 32 for fabricating the photomask blank; a treating unit34 (chamber, etc.) comprising a support 36 for the photomask blank, aheating element 38, a chill or cooling element 40, and anitrogen-purging apparatus 42; a processing unit 44 for patterning anddeveloping the photoresist layer; and a conveyor mechanism 46 forconducting the photomask blank through the system. The various units canbe electrically coupled to a microprocessor 48, which may be programmedto carry out particular functions as is known in the art. For example, abake unit such as a hotplate within a heating chamber (or chill platewithin a cooling chamber) can be connected to a controller such as acomputer or other processor to control the temperature of the plate,etc.

In one embodiment, depicted in FIG. 6A, the treating unit 34 isstructured with a temperature controlled plate support 36 whichtemperature can be elevated or lowered to function as a heating element38 and a cooling element 40, and a device 42 to purge nitrogen from thechamber 50. In a preferred embodiment, as depicted in FIG. 6B, thetreating unit 34′ can be structured with a bake unit in the form of ahotplate 38′ as a support 36′ for the photomask blank in the chamber50′, an interconnected chilling unit 40′ to cool the chamber 50′ to roomtemperature, and an interconnected device 42′ operable to provide anitrogen-purged atmosphere in the chamber 50′. In a simple application,the room temperature controlled chamber can provide both cooling and aN₂-purged environment.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. In a method of fabricating a photomask, prior to patterning theresist layer, dehydrating a layer of a chemically amplified resistdisposed on a photomask blank by heating the photomask blank on atemperature controlled substrate, and cooling the photomask blank toabout room temperature in an atmosphere purged of nitrogen.
 2. Themethod of claim 1, wherein the cooling step comprises maintaining thephotomask blank in said atmosphere for up to about 12 hours.
 3. Themethod of claim 1, wherein the cooling step comprises cooling thephotomask blank on a chill plate in said atmosphere for up to about 30minutes.
 4. In a method of fabricating a photomask, prior to patterningthe resist layer, treating a layer of a chemically amplified resistdisposed on a photomask blank by placing the photomask blank onto aheating plate in an environment purged of nitrogen for up to about 30minutes at a temperature of about 90–180° C. to dehydrate the resist. 5.In a method of fabricating a photomask, prior to patterning the resistlayer, treating a layer of a chemically amplified resist disposed on aphotomask blank by placing the photomask blank onto a heating plate forup to about 30 minutes at a temperature of about 90–180° C. to dehydratethe resist, and cooling the photomask blank to about room temperature inan atmosphere purged of nitrogen.
 6. In a method of fabricating aphotomask, prior to patterning the resist layer, treating a layer of achemically amplified resist disposed on a photomask blank by placing thephotomask blank into an atmosphere purged of nitrogen at above roomtemperature to dehydrate the chemically amplified photoresist layer. 7.In a method of fabricating a photomask, prior to patterning the resistlayer, dehydrating a layer of a chemically amplified resist disposed ona photomask blank by placing the photomask blank into an atmospherepurged of nitrogen at above room temperature.
 8. In a method offabricating a photomask, prior to patterning the resist layer,dehydrating a layer of a chemically amplified resist disposed on aphotomask blank by heating the photomask blank on a temperaturecontrolled substrate in an atmosphere purged of nitrogen.
 9. A method oftreating a chemically amplified resist-coated photomask blank,comprising the step of: prior to patterning the chemically amplifiedresist, heating the photomask blank to dehydrate the resist, and coolingthe photomask blank to about room temperature in a an atmosphere purgedof nitrogen.
 10. The method of claim 9, comprising heating the photomaskblank on a temperature-controlled plate to dehydrate the resist.
 11. Themethod of claim 9, comprising heating the photomask blank at about90–180° C. on a temperature-controlled plate for up to about 30 minutesto dehydrate the resist.
 12. The method of claim 9, comprising heatingthe photomask blank on a temperature-controlled plate at about 90–180°C. in an atmosphere purged of nitrogen for up to about 30 minutes todehydrate the resist.
 13. The method of claim 9, comprising cooling thephotomask blank an environment purged of nitrogen for about 6–12 hoursto about room temperature.
 14. The method of claim 9, comprising coolingthe photomask blank on a chill plate to about room temperature in anenvironment purged of nitrogen for about 10–30 minutes.
 15. A method oftreating a chemically amplified resist-coated photomask blank,comprising the step of: prior to patterning the resist, dehydrating theresist in an environment purged of nitrogen at above room temperature.16. A method of treating a chemically amplified resist-coated photomaskblank, comprising the step of: prior to patterning the resist,dehydrating the resist in an environment purged of nitrogen at atemperature of up to about 80° C. above room temperature.
 17. A methodof treating a chemically amplified resist-coated photomask blank,comprising the step of: prior to patterning the resist dehydrating theresist in an environment purged of nitrogen at a temperature of about21–100° C.
 18. A method of treating a chemically amplified resist-coatedphotomask blank, comprising the step of: prior to patterning the resist,dehydrating the resist in an environment purged of nitrogen at atemperature of about 21–100° C. for about 3–180 minutes.
 19. A method oftreating a chemically amplified resist-coated photomask blank,comprising the step of: storing the resist-coated photomask blank in acontainer purged of nitrogen maintained at a temperature of about21–100° C. to inhibit a decrease in dose sensitivity level of the resiston the photomask blank.
 20. A method of treating a photomask blankcomprising a chemically-amplified resist layer thereover, the methodcomprising the steps of: heating the photomask blank to dehydrate theresist layer; and cooling the photomask blank to about room temperaturesuch that the resist layer has an exposure sensitivity level at aboutthe same level as the resist layer when initially applied onto thephotomask blank.
 21. The method of claim 20, wherein the step of coolingthe photomask blank comprises placing the photomask blank on a substratehaving a temperature of about 20–25° C. for a time effective to cool thephotomask blank and resist layer.
 22. The method of claim 20, whereinthe photomask blank is cooled in an atmosphere purged of nitrogen. 23.The method of claim 20, wherein the step of cooling the photomask blankcomprises placing the photomask blank in an atmosphere purged ofnitrogen having a temperature of about 20–25° C. for a time effective tocool the photomask blank and resist layer.
 24. The method of claim 23,wherein the photomask blank is maintained said atmosphere for up toabout 12 hours.
 25. A method of treating a photomask blank comprising achemically-amplified resist layer thereover, the method comprising thestep of: heating the photomask blank to dehydrate the resist layer suchthat the resist layer has a dose sensitivity level at about the samelevel as the resist layer when initially applied onto the photomaskblank.
 26. The method of claim 25, wherein the photomask blank is heatedin an atmosphere purged of nitrogen at a temperature of about 21–100° C.27. The method of claim 25, wherein the step of heating the photomaskblank comprises placing the photomask blank on a substrate having atemperature of about 90–180° C. for a time effective to dehydrate theresist layer.
 28. The method of claim 27, wherein the photomask blank isplaced on the heated substrate for up to about 30 minutes.
 29. Themethod of claim 25, further comprising the step of cooling the photomaskblank and resin layer to a temperature of about 20–25° C.
 30. A methodof treating a photomask blank comprising a chemically-amplified resistlayer thereover, the method comprising the step of: placing thephotomask blank in a heated, atmosphere purged of nitrogen for a timeeffective to dehydrate the resist layer such that the resist layer hasan exposure sensitivity level at about the same level as the resistlayer when initially applied onto the photomask blank.
 31. The method ofclaim 30, wherein the photomask blank is heated to up to about 100° C.32. The method of claim 30, further comprising the step of cooling thephotomask blank and resin layer to a temperature of about 20–25° C. 33.A method of recovering exposure sensitivity of a chemically amplifiedresist disposed on a photomask blank from a post-coat delay effect,comprising the step of: heating the photomask blank to dehydrate theresist, and cooling the photomask blank in an environment purged ofnitrogen to about room temperature, such that the resist has a level ofexposure sensitivity approximate to the resist as when initially appliedonto the photomask blank.
 34. A method of recovering exposuresensitivity of a chemically amplified resist disposed on a photomaskblank from a post-coat delay effect, comprising the step of: heating thephotomask blank on a temperature-controlled substrate to dehydrate theresist, and cooling the photomask blank in an environment purged ofnitrogen to about room temperature, such that the resist has a level ofexposure sensitivity approximate to the resist as when initially appliedonto the photomask blank.
 35. A method of recovering exposuresensitivity of a chemically amplified resist disposed on a photomaskblank from a post-coat delay effect, comprising the step of: heating thephotomask blank on a temperature-controlled substrate at a temperatureof about 90–180° C. to dehydrate the resist, and cooling the photomaskblank in an environment purged of nitrogen to about room temperature,such that the resist has a level of exposure sensitivity approximate tothe resist as when initially applied onto the photomask blank.
 36. Amethod of recovering exposure sensitivity of a chemically amplifiedresist disposed on a photomask blank from a post-coat delay effect,comprising the step of: heating the photomask blank on atemperature-controlled substrate at a temperature of about 90–180° C. todehydrate the resist in an environment purged of nitrogen, and coolingthe photomask blank in an environment purged of nitrogen to about roomtemperature, such that the resist has a level of exposure sensitivityapproximate to the resist as when initially applied onto the photomaskblank.
 37. A method of recovering exposure sensitivity of a chemicallyamplified resist disposed on a photomask blank from a post-coat delayeffect, comprising the step of: heating the photomask blank on atemperature-controlled substrate at a temperature of about 90–180° C. todehydrate the resist, and cooling the photomask blank to about roomtemperature for about 6–12 hours in an environment purged of nitrogen,such that the resist has a level of exposure sensitivity approximate tothe resist as when initially applied onto the photomask blank.
 38. Amethod of recovering exposure sensitivity of a chemically amplifiedresist disposed on a photomask blank from a post-coat delay effect,comprising the step of: heating the photomask blank on atemperature-controlled substrate at a temperature of about 90–180° C. todehydrate the resist, and cooling the photomask blank on a chill plateto about room temperature in an environment purged of nitrogen, suchthat the resist has a level of exposure sensitivity approximate to theresist as when initially applied onto the photomask blank.
 39. A methodof recovering exposure sensitivity of a chemically amplified resistdisposed on a photomask blank from a post-coat delay effect, comprisingthe steps of: heating the photomask blank on a temperature-controlledsubstrate at a temperature of about 90–180° C. to dehydrate the resistsuch that the resist has an exposure sensitivity at a level approximateto the resist when initially applied onto the photomask blank; andcooling the photomask blank in an environment purged of nitrogen toabout room temperature.
 40. A method of recovering exposure sensitivityof a chemically amplified resist disposed on a photomask blank from apost-coat delay effect, comprising the step of: heating the photomaskblank in an environment purged of nitrogen at above room temperature todehydrate the resist, and cooling the photomask blank in an environmentpurged of nitrogen to about room temperature, such that the resist has alevel of exposure sensitivity approximate to the resist as wheninitially applied onto the photomask blank.
 41. A method of recoveringexposure sensitivity of a chemically amplified resist disposed on aphotomask blank from a post-coat delay effect, comprising the step of:heating the photomask blank in an environment purged of nitrogen at atemperature of up to about 80° C. above room temperature to dehydratethe resist, and cooling the photomask blank in an environment purged ofnitrogen to about room temperature, such that the resist has a level ofexposure sensitivity approximate to the resist as when initially appliedonto the photomask blank.
 42. A method of recovering exposuresensitivity of a chemically amplified resist disposed on a photomaskblank from a post-coat delay effect, comprising the step of: heating thephotomask blank in an environment purged of nitrogen at a temperature ofabout 21 to about 100° C. to dehydrate the resist, and cooling thephotomask blank in an environment purged of nitrogen to about roomtemperature, such that the resist has a level of exposure sensitivityapproximate to the resist as when initially applied onto the photomaskblank.
 43. A method of recovering exposure sensitivity of a chemicallyamplified resist disposed on a photomask blank from a post-coat delayeffect, comprising the step of: heating the photomask blank in anenvironment purged of nitrogen at a temperature of about 21–100° C. todehydrate the resist for about 3–180 minutes, and cooling the photomaskblank in an environment purged of nitrogen to about room temperature,such that the resist has a level of exposure sensitivity approximate tothe resist as when initially applied onto the photomask blank.
 44. Amethod of recovering exposure sensitivity of a chemically amplifiedresist disposed on a photomask blank from a post-coat delay effect,comprising the steps of: storing the photomask blank in an environmentpurged of nitrogen at a temperature of about 21–100° C. to dehydrate theresist and maintain the exposure sensitivity of the resist at a levelapproximate to the resist when initially applied onto the photomaskblank; and cooling the photomask blank in an environment purged ofnitrogen to about room temperature.
 45. A method of treating a photomaskblank having a chemically-amplified resist layer thereover, comprisingthe steps of: heating a photomask blank comprising an overlying layer ofa chemically amplified resist, on a heating plate at about 90–180° C. todehydrate the resist; and cooling the photomask blank to about roomtemperature in a container purged of nitrogen.
 46. A method of treatinga photomask blank having a chemically-amplified resist layer thereover,comprising the steps of heating an photomask blank comprising anoverlying layer of a chemically amplified resist, in an environmentpurged of nitrogen on a heating plate at about 90–180° C. to dehydratethe resist; and cooling the photomask blank to about room temperature ina nitrogen-purged environment.
 47. A method of treating a photomaskblank having a chemically-amplified resist layer thereover, comprisingthe steps of: placing a photomask blank comprising an overlying layer ofa chemically amplified resist, into an environment purged of nitrogen atabove room temperature to dehydrate the resist layer; and cooling theresist layer to about room temperature.